The Macular Photocoagulation Study is a multi-center collaborative trial of the photocoagulation of subretinal neovascular membranes in senile macular degeneration and presumed ocular histoplasmosis. The objectives in presumed ocular histoplasmosis are: A) To determine by means of a randomized controlled clinical trial whether Argon laser photocoagulation is a benefit in preventing visual acuity loss in eyes with presumed ocular histoplasmosis and a neovascular membrane 200 to 1,500 microns from the center of the fovea. B) To document the natural history of choroidal neovascular membranes in the macula in the fellow eye in presumed ocular histoplasmosis syndrome with particular reference to subfoveal neovascular membranes to determine the feasibility of commencing and randomizing clinical trials for this latter group of eyes. C) To define precisely the risk of development of symptomatic choroidal neovascular membranes from an atrophic scar (Histo spots) in the macula of the fellow eye. The objectives in senile macular degeneration are: A) To evaluate by means of a randomized clinical trial, the role of Argon laser photocoagulation in the management of choroidal neovascular membranes between 200 and 1,500 microns from the fovea. B) To determine the natural history of subfoveal neovascular membranes in the fellow eye of patients with senile maculopathy with a view to considering a randomized clinical trial of photocoagulation for subfoveal neovascular membranes. C) To describe precisely and quantitatively the natural history of drusen in Bruch's membrane with partial reference to the risk of developing serious detachments of the retinal pigment epithelium (Avascular disciform) in eyes with senile macular degeneration, to consider a randomized trial for such eyes.